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SQL to find the number of distinct values in a column
...aggregate function:
SELECT COUNT(DISTINCT column_name) AS some_alias FROM table_name
This will count only the distinct values for that column.
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Parse JSON in TSQL
...le Talk website that outlines how to take a JSon string and output it into tables and columns that can be queried. This is for SQL Server 2016: https://www.simple-talk.com/sql/learn-sql-server/json-support-in-sql-server-2016/
– codeaf
Jul 28 '16 at 18:10
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PostgreSQL: Difference between text and varchar (character varying)
...ange the limit in live environment (requires exclusive lock while altering table)
varchar – just like text
text – for me a winner – over (n) data types because it lacks their problems, and over varchar – because it has distinct name
The article does detailed testing to show that the...
Is there any performance gain in indexing a boolean field?
...is is not entirely correct, without an index mySql needs to scan the whole table to find the relevant rows.
– ilanco
May 9 '12 at 22:04
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Select statement to find duplicates on certain fields
...ltiple records, you can use..
select field1,field2,field3, count(*)
from table_name
group by field1,field2,field3
having count(*) > 1
Check this link for more information on how to delete the rows.
http://support.microsoft.com/kb/139444
There should be a criterion for deciding how you defi...
How do I create a PDO parameterized query with a LIKE statement?
...t out right after I posted:
$query = $database->prepare('SELECT * FROM table WHERE column LIKE ?');
$query->execute(array('value%'));
while ($results = $query->fetch())
{
echo $results['column'];
}
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Check if a row exists, otherwise insert
I need to write a T-SQL stored procedure that updates a row in a table. If the row doesn't exist, insert it. All this steps wrapped by a transaction.
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Specify custom Date format for colClasses argument in read.table/read.csv
... way to specify the Date format when using the colClasses argument in read.table/read.csv?
4 Answers
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Sequelize Unknown column '*.createdAt' in 'field list'
...he error is that you have timestamps enabled in sequelize, but your actual table definitions in the DB do not contain a timestamp column.
When you do user.find it will just do SELECT user.*, which only takes the columns you actually have. But when you join, each column of the joined table will be a...
Is an index needed for a primary key in SQLite?
When an integer column is marked as a primary key in an SQLite table, should an index be explicitly created for it as well? SQLite does not appear to automatically create an index for a primary key column, but perhaps it indexes it anyway, given its purpose? (I will be searching on that column all t...